1. Technical Field
The present invention relates to a cassette loading station for semiconductor processing equipment. More particularly, the present invention relates to an ergonomic cassette loading station for automatically placing a cassette at a processing equipment loading port.
2. Description of the Prior Art
As knowledge is gained concerning hazards in the workplace, such hazards should, if possible, be immediately eliminated. It is also important to identify the potential for such hazards before any injuries can occur. For example, industry is presently concerned with repetitive stress syndrome and the use of ergonomic design to avoid repetitive body movements that may result in long term disability that is associated with repetitive stress syndrome.
Modern semiconductor process equipment is adapted to receive a cassette of semiconductor substrates. The cassette is loaded by an equipment operator. A cassette may contain anywhere from one to twenty-six or more substrates, may weigh up to 3.7 kilograms (10 pounds) or more, and may contain finished product having a value of $US 1 million or more.
A standard cassette is used to transfer semiconductor substrates, in which the substrates are positioned in a vertical orientation. The wafers are positioned within the cassette on parallel slots, tracks, or grooves on opposing sides of the cassette for transport in a vertical orientation to minimize the likelihood of contaminating particles settling on the wafer surface. The cassette itself is placed within a sealed environment when it is transported to reduce wafer exposure to contaminants within the ambient. The cassette has an opening at a top portion thereof through which the substrates are loaded and unloaded.
FIG. 1 is a perspective view of a multi-chamber semiconductor processing system 11 having two cassette loading ports 17, 19. To load the cassette into a typical substrate processing environment, the operator places the cassette into a loading position by extending his arms into the equipment while holding the cassette, and then rotates the cassette through about 90.degree. of movement about a horizontal axis in front of the operator, such that the substrates are moved to a horizontal orientation for loading to, and unloading from, the process environment by a robot arm located within the process environment at the cassette loading port. The wafers are positioned in a horizontal position for loading and unloading to allow a robot to index the wafers within the context of a standard processing environment. Such rotation is therefore necessary to index and clamp the cassette in proper alignment with the process equipment.
An operator may load and unload a cassette in this manner 50-60 times during a typical work shift. It is thought that maximum ulnar deviation of the wrist should preferably not exceed 30.degree.. Some believe that repetitive ulnar deviation of an operator's wrist at 90.degree. may in time result in a repetitive stress injury. In view of the value of the substrates contained in the cassette, and the operator's awareness of this fact, it is not unreasonable to expect that the operator exerts significant pressure on the cassette to prevent dropping it, possibly increasing the stress placed on his wrists.
It is therefore important that ergonomic design for process equipment, especially where such machinery is repetitively loaded and unloaded by an operator, be pursued if industry is to continue the laudable goal of improving workplace safety.